`fp2ulp``x2``x1`procedure`fp2ulp-error``x2``x1``r`procedure- x2
- flonum
- x1
- flonum
- r
- flonum

Like

`fpulp`and`fpulp-error`, but for double-double flonums.The unit in last place of a double-double is that of the higher-order of the pair, shifted 52 bits right.

Examples:

> (fp2ulp 1.0 0.0) 4.930380657631324e-32 > (let-values ([(x2 x1) (fl2 1/7)]) (fp2ulp-error x2 x1 1/7)) 0.07142857142857142